steve H wrote in message
...
Hi,

Can anyone find the spec or equivalent for a mullard YL1321, looks like
the same pinout as the
4cx250/350 family but conduction cooled. The main concern is the heater
voltage, usually 6.3 or
26.5. I have tried the usual google etc and its not in any of my data
books.
Put 6.0 (not 6.3)V on the heater pins and see if it draws the right sort of
current - if it's a higher voltage version, you won't do any harm. I don't
know of any variants that ran at lower voltage.

Steve